From what I'm hearing that's about the right cost per lead in my market place. 

When important, send by certified mail.

Send it certified, return receipt requested, so that you have a signature.

You could also join BP as a pro member and post your deal or your request for buyers in the marketplace forum.

We think there are still good deals out there to be found, and having the right systems in place and continuing to nurture relationships in the marketplace allow us to uncover them.

However, I didn't notice too much in the marketplace area for my State.

Unfortunately, I have not been seeing much value in the market place of late.

start fully documenting everything and take lots of pictures, I would start communicating via email or by letter, even send them a certified letter stating damages etc, sounds like you didn't hire a qualified roofer. send a copy of everything to your attorney maybe even have him draft a letter demanding a response, if push for a refund + damages and go with a new roofer

Should I send a certified letter as well?

(also, I am looking for a mentor in all types of investment) You found the place,  just simply go to the BP marketplace or call your local REIA they will be able to give you a name or two of someone who is at the event every month pushing hard money on folks :)